io_uring/tctx.c

// SPDX-License-Identifier: GPL-2.0
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/file.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/nospec.h>
#include <linux/io_uring.h>

#include <uapi/linux/io_uring.h>

#include "io_uring.h"
#include "tctx.h"
#include "bpf_filter.h"

static struct io_wq *io_init_wq_offload(struct io_ring_ctx *ctx,
					struct task_struct *task)
{
	struct io_wq_hash *hash;
	struct io_wq_data data;
	unsigned int concurrency;

	mutex_lock(&ctx->uring_lock);
	hash = ctx->hash_map;
	if (!hash) {
		hash = kzalloc_obj(*hash);
		if (!hash) {
			mutex_unlock(&ctx->uring_lock);
			return ERR_PTR(-ENOMEM);
		}
		refcount_set(&hash->refs, 1);
		init_waitqueue_head(&hash->wait);
		ctx->hash_map = hash;
	}
	mutex_unlock(&ctx->uring_lock);

	data.hash = hash;
	data.task = task;

	/* Do QD, or 4 * CPUS, whatever is smallest */
	concurrency = min(ctx->sq_entries, 4 * num_online_cpus());

	return io_wq_create(concurrency, &data);
}

void io_uring_free_tctx(struct task_struct *tsk)
{
	struct io_uring_task *tctx = tsk->io_uring;
	struct io_tctx_node *node;
	unsigned long index;

	/*
	 * Fault injection forcing allocation errors in the xa_store() path
	 * can lead to xa_empty() returning false, even though no actual
	 * node is stored in the xarray. Until that gets sorted out, attempt
	 * an iteration here and warn if any entries are found.
	 */
	if (tctx) {
		xa_for_each(&tctx->xa, index, node) {
			WARN_ON_ONCE(1);
			break;
		}
		WARN_ON_ONCE(tctx->io_wq);
		WARN_ON_ONCE(tctx->cached_refs);

		percpu_counter_destroy(&tctx->inflight);
		kfree(tctx);
		tsk->io_uring = NULL;
	}
}

void __io_uring_free(struct task_struct *tsk)
{
	io_uring_free_tctx(tsk);
	if (tsk->io_uring_restrict) {
		io_put_bpf_filters(tsk->io_uring_restrict);
		kfree(tsk->io_uring_restrict);
		tsk->io_uring_restrict = NULL;
	}
}

__cold struct io_uring_task *io_uring_alloc_task_context(struct task_struct *task,
							struct io_ring_ctx *ctx)
{
	struct io_uring_task *tctx;
	int ret;

	tctx = kzalloc_obj(*tctx);
	if (unlikely(!tctx))
		return ERR_PTR(-ENOMEM);

	ret = percpu_counter_init(&tctx->inflight, 0, GFP_KERNEL);
	if (unlikely(ret)) {
		kfree(tctx);
		return ERR_PTR(ret);
	}

	tctx->io_wq = io_init_wq_offload(ctx, task);
	if (IS_ERR(tctx->io_wq)) {
		ret = PTR_ERR(tctx->io_wq);
		percpu_counter_destroy(&tctx->inflight);
		kfree(tctx);
		return ERR_PTR(ret);
	}

	tctx->task = task;
	xa_init(&tctx->xa);
	init_waitqueue_head(&tctx->wait);
	atomic_set(&tctx->in_cancel, 0);
	atomic_set(&tctx->inflight_tracked, 0);
	mpscq_init(&tctx->task_list, &tctx->task_head);
	INIT_WORK(&tctx->fallback_work, io_tctx_fallback_work);
	init_task_work(&tctx->task_work, tctx_task_work);
	return tctx;
}

static int io_tctx_install_node(struct io_ring_ctx *ctx,
				struct io_uring_task *tctx)
{
	struct io_tctx_node *node;
	int ret;

	if (xa_load(&tctx->xa, (unsigned long)ctx))
		return 0;

	node = kmalloc_obj(*node);
	if (!node)
		return -ENOMEM;
	node->ctx = ctx;
	node->task = current;

	ret = xa_err(xa_store(&tctx->xa, (unsigned long)ctx,
				node, GFP_KERNEL));
	if (ret) {
		kfree(node);
		return ret;
	}

	mutex_lock(&ctx->tctx_lock);
	list_add(&node->ctx_node, &ctx->tctx_list);
	mutex_unlock(&ctx->tctx_lock);
	return 0;
}

int __io_uring_add_tctx_node(struct io_ring_ctx *ctx)
{
	struct io_uring_task *tctx = current->io_uring;
	bool new_tctx = false;
	int ret;

	if (unlikely(!tctx)) {
		tctx = io_uring_alloc_task_context(current, ctx);
		if (IS_ERR(tctx))
			return PTR_ERR(tctx);
		new_tctx = true;

		if (data_race(ctx->int_flags) & IO_RING_F_IOWQ_LIMITS_SET) {
			unsigned int limits[2];

			mutex_lock(&ctx->uring_lock);
			limits[0] = ctx->iowq_limits[0];
			limits[1] = ctx->iowq_limits[1];
			mutex_unlock(&ctx->uring_lock);

			ret = io_wq_max_workers(tctx->io_wq, limits);
			if (ret)
				goto err_free;
		}
	}

	/*
	 * Re-activate io-wq keepalive on any new io_uring usage. The wq may have
	 * been marked for idle-exit when the task temporarily had no active
	 * io_uring instances.
	 */
	if (tctx->io_wq)
		io_wq_set_exit_on_idle(tctx->io_wq, false);

	if (new_tctx)
		current->io_uring = tctx;

	ret = io_tctx_install_node(ctx, tctx);
	if (!ret)
		return 0;
err_free:
	if (new_tctx) {
		current->io_uring = NULL;
		if (tctx->io_wq) {
			io_wq_exit_start(tctx->io_wq);
			io_wq_put_and_exit(tctx->io_wq);
		}
		percpu_counter_destroy(&tctx->inflight);
		kfree(tctx);
	}
	return ret;
}

int __io_uring_add_tctx_node_from_submit(struct io_ring_ctx *ctx)
{
	int ret;

	if (ctx->flags & IORING_SETUP_SINGLE_ISSUER
	    && ctx->submitter_task != current)
		return -EEXIST;

	ret = __io_uring_add_tctx_node(ctx);
	if (ret)
		return ret;

	current->io_uring->last = ctx;
	return 0;
}

/*
 * Remove this io_uring_file -> task mapping.
 */
__cold void io_uring_del_tctx_node(unsigned long index)
{
	struct io_uring_task *tctx = current->io_uring;
	struct io_tctx_node *node;

	if (!tctx)
		return;
	node = xa_erase(&tctx->xa, index);
	if (!node)
		return;

	WARN_ON_ONCE(current != node->task);
	WARN_ON_ONCE(list_empty(&node->ctx_node));

	mutex_lock(&node->ctx->tctx_lock);
	list_del(&node->ctx_node);
	mutex_unlock(&node->ctx->tctx_lock);

	if (tctx->last == node->ctx)
		tctx->last = NULL;
	kfree(node);

	if (xa_empty(&tctx->xa) && tctx->io_wq)
		io_wq_set_exit_on_idle(tctx->io_wq, true);
}

__cold void io_uring_clean_tctx(struct io_uring_task *tctx)
{
	struct io_wq *wq = tctx->io_wq;
	struct io_tctx_node *node;
	unsigned long index;

	xa_for_each(&tctx->xa, index, node) {
		io_uring_del_tctx_node(index);
		cond_resched();
	}
	if (wq) {
		/*
		 * Must be after io_uring_del_tctx_node() (removes nodes under
		 * uring_lock) to avoid race with io_uring_try_cancel_iowq().
		 */
		io_wq_put_and_exit(wq);
		tctx->io_wq = NULL;
	}
}

void io_uring_unreg_ringfd(void)
{
	struct io_uring_task *tctx = current->io_uring;
	int i;

	for (i = 0; i < IO_RINGFD_REG_MAX; i++) {
		if (tctx->registered_rings[i]) {
			fput(tctx->registered_rings[i]);
			tctx->registered_rings[i] = NULL;
		}
	}
}

int io_ring_add_registered_file(struct io_uring_task *tctx, struct file *file,
				     int start, int end)
{
	int offset, idx;
	for (offset = start; offset < end; offset++) {
		idx = array_index_nospec(offset, IO_RINGFD_REG_MAX);
		if (tctx->registered_rings[idx])
			continue;

		tctx->registered_rings[idx] = file;
		return idx;
	}
	return -EBUSY;
}

static int io_ring_add_registered_fd(struct io_uring_task *tctx, int fd,
				     int start, int end)
{
	struct file *file;
	int offset;

	file = fget(fd);
	if (!file) {
		return -EBADF;
	} else if (!io_is_uring_fops(file)) {
		fput(file);
		return -EOPNOTSUPP;
	}
	offset = io_ring_add_registered_file(tctx, file, start, end);
	if (offset < 0)
		fput(file);
	return offset;
}

/*
 * Register a ring fd to avoid fdget/fdput for each io_uring_enter()
 * invocation. User passes in an array of struct io_uring_rsrc_update
 * with ->data set to the ring_fd, and ->offset given for the desired
 * index. If no index is desired, application may set ->offset == -1U
 * and we'll find an available index. Returns number of entries
 * successfully processed, or < 0 on error if none were processed.
 */
int io_ringfd_register(struct io_ring_ctx *ctx, void __user *__arg,
		       unsigned nr_args)
{
	struct io_uring_rsrc_update __user *arg = __arg;
	struct io_uring_rsrc_update reg;
	struct io_uring_task *tctx;
	int ret, i;

	if (!nr_args || nr_args > IO_RINGFD_REG_MAX)
		return -EINVAL;

	mutex_unlock(&ctx->uring_lock);
	ret = __io_uring_add_tctx_node(ctx);
	mutex_lock(&ctx->uring_lock);
	if (ret)
		return ret;

	tctx = current->io_uring;
	for (i = 0; i < nr_args; i++) {
		int start, end;

		if (copy_from_user(&reg, &arg[i], sizeof(reg))) {
			ret = -EFAULT;
			break;
		}

		if (reg.resv) {
			ret = -EINVAL;
			break;
		}

		if (reg.offset == -1U) {
			start = 0;
			end = IO_RINGFD_REG_MAX;
		} else {
			if (reg.offset >= IO_RINGFD_REG_MAX) {
				ret = -EINVAL;
				break;
			}
			start = reg.offset;
			end = start + 1;
		}

		ret = io_ring_add_registered_fd(tctx, reg.data, start, end);
		if (ret < 0)
			break;

		reg.offset = ret;
		if (copy_to_user(&arg[i], &reg, sizeof(reg))) {
			fput(tctx->registered_rings[reg.offset]);
			tctx->registered_rings[reg.offset] = NULL;
			ret = -EFAULT;
			break;
		}
	}

	return i ? i : ret;
}

int io_ringfd_unregister(struct io_ring_ctx *ctx, void __user *__arg,
			 unsigned nr_args)
{
	struct io_uring_rsrc_update __user *arg = __arg;
	struct io_uring_task *tctx = current->io_uring;
	struct io_uring_rsrc_update reg;
	int ret = 0, i;

	if (!nr_args || nr_args > IO_RINGFD_REG_MAX)
		return -EINVAL;
	if (!tctx)
		return 0;

	for (i = 0; i < nr_args; i++) {
		if (copy_from_user(&reg, &arg[i], sizeof(reg))) {
			ret = -EFAULT;
			break;
		}
		if (reg.resv || reg.data || reg.offset >= IO_RINGFD_REG_MAX) {
			ret = -EINVAL;
			break;
		}

		reg.offset = array_index_nospec(reg.offset, IO_RINGFD_REG_MAX);
		if (tctx->registered_rings[reg.offset]) {
			fput(tctx->registered_rings[reg.offset]);
			tctx->registered_rings[reg.offset] = NULL;
		}
	}

	return i ? i : ret;
}

int __io_uring_fork(struct task_struct *tsk)
{
	struct io_restriction *res, *src = tsk->io_uring_restrict;

	/* Don't leave it dangling on error */
	tsk->io_uring_restrict = NULL;

	res = kzalloc_obj(*res, GFP_KERNEL_ACCOUNT);
	if (!res)
		return -ENOMEM;

	tsk->io_uring_restrict = res;
	io_restriction_clone(res, src);
	return 0;
}